BAJA Korg CX3 Rotary Effect

bajaman · Post by **bajaman** » 14 Feb 2008, 21:02

Hey hey Andre

Great news and thanks for the mods info

This is exactly why freestompboxes is THE best place on the web - I posted this project and many have suggested mods, and now Andre has built one and suggested some very good mods and corrections - I especially like the slower ramp down time for the horn section

Thanks again Andre for your research - glad to hear you like it for a guitar effect - me too

cheers
bajaman

OrionManMatt · Post by **OrionManMatt** » 27 Feb 2008, 17:42

Still waiting on those sound clips.

Great work, Bajaman! Just begs for an expression pedal and a Micro POG....

andre · Post by **andre** » 27 Mar 2008, 11:50

Here's a soundclip I did using my Tele and my brand new Hughes & Kettner Statesman Quad.
http://www.xs4all.nl/~jvcn0028/CX-3%20L ... mo%201.mp3

The sounclip is not really loud so you might need to turn up your volume.

I did some more mods to improve the quality.
I changed the 100k resistor between pins 1 & 2 of the opamp to a 47k as suggested by bajaman to get more unity gain.
After this I thought the rotor effect was too soft, so I changed the 47k resistor after the Rotor's low pass filter to 22k.

I also replaced the 2k2 resistors connected to the outputs of the BBD's for 4k7 trimmers to reduce clock noise.

André

sosodef · Post by **sosodef** » 27 Mar 2008, 13:06

can you use the new cool audio chips for these?

andre · Post by **andre** » 27 Mar 2008, 14:17

sosodef wrote:can you use the new cool audio chips for these?

You probably can, but not without the necessary alterations to the PCB, and you also have to change the powersupply from
12V to 9V.
As mentioned earlier in this thread, you can also use MN3007 instead of MN3004 with only minor adjustments to the circuit.
You can order MN3007's from Smallbear.

andre · Post by **andre** » 27 Mar 2008, 14:22

Here's another soundclip:
http://www.xs4all.nl/~jvcn0028/CX-3_demo2.mp3

Later on I will see if I can do one with a bit of overdrive.

André

OrionManMatt · Post by **OrionManMatt** » 27 Mar 2008, 15:06

andre wrote:Here's another soundclip:
http://www.xs4all.nl/~jvcn0028/CX-3_demo2.mp3

Later on I will see if I can do one with a bit of overdrive.

André

Nice playing. Liked the single coil tone. Though it was less obvious that it was on when your playing was more staccato, I found the slightly phasey rotary effect to be nice to the ears. A bit of overdrive would be cool too.

Thanks for taking the time to do this. I wonder how this compares to other rotary stompboxes out there? I'm not too familiar with the options outside of the Boss Rotosphere and the BBE SoulVibe (more UniVibe-y, I know)

IggY · Post by **IggY** » 24 Apr 2008, 13:47

Stephengiles wrote:Many thanks, I'm sure that I've seen those circuits somewhere else - on a French site maybe??

It was a Canadians link on the Hawaaian forum to a French site:
https://www.diystompboxes.com/smfforum/ ... opic=25130
about 4 years ago.
The whole service map is there.

gght · Post by **gght** » 16 Jun 2009, 23:41

Is it likely that this is the circuit that morphed into the Korg g4 pedal?? Also, this seems to be similar to the Dynacord cls-222, I am told it also uses 2 BBD lines. Anyone know??

Thanks!
Dave

station · Post by **station** » 17 Jun 2009, 23:52

Found the schematic over here:
http://www.geocities.com/diygescorp/cls222_1.jpg
http://www.geocities.com/diygescorp/cls222_2.jpg

station · Post by **station** » 30 Jul 2009, 15:34

Hey Baja - Correct me if I'm wrong, but aren't the diodes in the bridge rectifier wired the wrong way around?

In yours, the junction of the anodes connects to the positive DC supply.

I tried this and I nearly blew up the 2200 uf cap. So I tried flipping the diodes around and it worked fine.

Normally, it's the cathode junction that supplies positive DC voltage right?

Like this:

IggY · Post by **IggY** » 31 Jul 2009, 06:30

station wrote:Hey Baja - Correct me if I'm wrong, but aren't the diodes in the bridge rectifier wired the wrong way around?

In yours, the junction of the anodes connects to the positive DC supply.

I tried this and I nearly blew up the 2200 uf cap. So I tried flipping the diodes around and it worked fine.

Normally, it's the cathode junction that supplies positive DC voltage right?

Like this:

don`t let the plus-signs mislead you, but read his explanations in this thread:
viewtopic.php?f=13&t=395&p=33920&hilit=anode#p33920

station · Post by **station** » 30 Aug 2009, 19:21

It's not boxed up yet, but I finished the circuit for my own Baja CX-3 Leslie simulator and I have to say i love it. It sounds really smooth and with some mods the eq is very natural and complimentary to the guitar. I used MN3007 chips I got on Ebay from hongkongsuperseller. I was never able to get my hands on a 16V AC adapter, so I'm running a 12 DC wall wart to the DC output points on the rectifier and It works fine. Here's what I did for mods:

-The frequency response mod mentioned by analog guru on page 3 of this thread.
-750pf for the clock timer caps (-a must with the 3007 chips).
-Changed the 100k resistor across the 4558 for a 68k because I like a little boost on the effect, but not as much as the 100k was giving.
-Changed the low frequency (rotor) mixing resistor (R97) from 47k to 22k to increase the rotor volume
-Changed the high frequency (horn) mixing resistor (R94) from 200k to 330k to decrease the horn volume
(These last three resistor mods can be done with trimpots or even external pots to fine tune the balance of the dry, rotor, and horn elements)
-Changed the 3.3k resistor in the HF ramp up/down section (R47) to a 47k (like Andre said, I think the schematic calls for a 33k, but you can adjust to taste.)
-I've thought about changing the resistors around the frequency adjust trimpots (R103 and R106) and making them into external controls to have a wider high speed control on the outside of the box. I'll keep you posted.
-I think Bajaman mentioned which resistors control the slow speed too, so they could also be put on pots.
-Build to specs, the high frequency modulation (the horn) is a bit wide so I did what Andre suggested and a low pass filter at pin 9 of the 4046 (the right side of the component side of the board). This helped a lot and I was able to dial in a more subtle effect.

Still, it is useful to have the wide modulation too - you can get some great wobbly organ sounds. (by the way for you baseball fans, the classic dum dum dum dum - dum dum dum dum dudududududu Charge! is hilarious) Anyway, here are some sound clips http://www.soundclick.com/bands/default ... tent=music The first one is with the horn modulation depth backed off a bit, and second two are full on. The last one has the depth up almost all the way. I think this setting is my favorite.

If you are looking for a rewarding but time consuming project I would recommend this one. Thanks to Bajaman for putting this whole thing together and making it available to the stompbox community.

madbean · Post by **madbean** » 30 Aug 2009, 19:54

Oh man, that sounds great, Station! I know what I'll be doing over the next week or two now. Thanks for the soundclips and build report.

station · Post by **station** » 16 Sep 2009, 00:00

No problem Madbean. Let me know how it goes if you decide to bite the bullet.

I finally got around to getting a 1790. Here's what I did with the box:

borislavgajic · Post by **borislavgajic** » 16 Sep 2009, 07:46

nice nice......

boris

marin · Post by **marin** » 05 Jul 2010, 12:58

beautiful!

atreidesheir · Post by **atreidesheir** » 31 Jul 2010, 18:50

anyone have and od recommendation to put on the end the circuit?

I was thinking of putting the peppermill od after it. It is light and transparent and very organic sounding.

subtle like the 1960s leslie at my church.

artcool · Post by **artcool** » 11 Mar 2011, 14:45

Hi,
i'm new here and may be i can get help on this issue..

i own a vintage Korg CX-3 in which the leslie simulator now is working only in the bass component (low frenquency rotary drum simulation is ok), but the upper part is passing by with no effect at all...just the litlle volume drop when engaging the Rotary Simulator, but no modulation in the "upper rotor"...

Any clue on where to start looking this failure in the KLM-246 board? could be the MN3004 ICs? the frequency crossover components?

thank you in advance.

bajaman · Post by **bajaman** » 11 Mar 2011, 20:45

look for leaking electrolytics

bajaman

BAJA Korg CX3 Rotary Effect [documentation]